Hi Ferrero,
I do see a problem here! The 433 MHz ISM Band allows you to transmitt between 433,05 MHz and 434,79 MHz. That means, that any LoRa chirp should not exceed that frequency range!
For the lower end 433,05 MHz that means that the lowest frequency you are allowed to set up is 433,050+BW/2. For BW125: 433.050+0,0625MHz = 433,1125 MHz.
For the upper end 434,790 MHz that means that the highest frequency you are allowd to set up is 434,790-BW/2. For BW125: 434,790-0,0625MHz = 434,7275 MHz
So, Frequency 4 is out of band, while on the other side you could go further up to 434,700 MHz.
Why not using 433,2 / ,4 / ,6 / ,8 / 434,0 / ,2 / ,4 / ,6 ?
It’s the same number of channels, but its in-band and keeps enough distance from the band-limits.